Gill is the final boss in Street Fighter III: 3rd Strike. In the game's single-player arcade mode, players normally face Gill after their character-specific rival, making him the climactic opponent for nearly the entire roster.
Gill leads the Illuminati, the secret organization that drives much of Street Fighter III's storyline. His unusual red-and-blue body reflects his elemental powers: he can use fire and ice attacks, and his Resurrection ability can restore him after he has been defeated if the player fails to finish the fight decisively.
His boss design also explains why he is often remembered as one of the series' most demanding opponents. Gill has powerful attacks, strong defensive options, and access to the Seraphic Wing Super Art, a cinematic move that can punish careless play. He is not simply another tournament fighter; he is an unplayable boss in the original arcade version.
The main exception is Gill himself: when selected in versions that allow it, his final opponent is Alex rather than another Gill mirror match.